AGR Deactivation: Questions & Answers for TDI

Hi fellow DIY enthusiasts!

I'm curious to know if the increased combustion chamber temperatures after the deactivation of the EGR system, especially during partial load operation (particularly with fuel-efficient driving), reduce the engine lifespan? In older diesel generations, the generally higher temperatures in the piston area often led to head gasket failure at 130,000-170,000 km. In my case, installing a larger radiator significantly extended that interval. What do you think about this link?
http://f23.parsimony.net/forum52632/messages/44929.htm
How about the turbocharger? Doesn't it spin faster in the partial load range (more fresh air intake, more rpm/km) -> leading to faster wear? Thank you in advance .

Best regards, Christian.

Hello,

Sorry, that post in the BMW forum is complete nonsense.
The thermal stress on the piston crown is greatest at full load, and at this point, the EGR system is typically deactivated.
Even the turbocharger's speed changes only slightly with or without EGR. Because as soon as significant boost pressure is built up, it is necessary for the EGR valve to close, so that all the compressed air doesn't get blown directly into the exhaust.

Best regards, Rainer.

Hi Rainer!

Then, even with that, the thermal stress on the pistons, etc., at a driving speed between 1000 and 2500 rpm should correspond to that at 4500 to 5000 rpm, which could certainly also lead to increased wear??? I'm curious to know if perhaps only the air cushion in the combustion chamber becomes a little hotter, but the material itself doesn't????? I want to reach 350,000 km (currently 174,000 km on the 1Z). Otherwise, I'll put the good old TD engines in the new models in the future .

Best regards, Christian.

haehnlein wrote:

Then, even so, the thermal stress on the pistons, etc., at an engine speed between 1000 and 2500 rpm should correspond to that at 4500 to 5000 rpm, which could certainly also lead to increased wear??? I'm curious whether perhaps only the air cushion in the combustion chamber becomes slightly hotter, but the material itself doesn't?????

Hi Christian,

In systems where the injection quantity is controlled by the injection duration, the combustion process is inevitably shorter at partial load.

A shorter combustion process, of course, "fades" more quickly, meaning that less heat can reach the pistons and other components due to the shorter duration, compared to full load operation.

Therefore, if the combustion, without EGR and with a "particularly lean" mixture, can potentially be even hotter in certain areas (but only for a short time and within the area of the injector nozzle) than at full load with a less lean mixture, the thermal stress on the material is, in my opinion, certainly lower at full load.

Sure,
Diesel fuel, as is well known, burns inhomogeneously. This means that the injected fuel forms small droplets that evaporate and combust from the outside in. In the immediate vicinity of these droplets, the temperature is always very high, which, under partial load conditions, causes oxygen and nitrogen from the abundant air to form nitrogen oxides.
The overall temperature depends only on the energy input (amount of diesel multiplied by its calorific value) and the heat capacity of the cylinder contents. It is possible to calculate the actual temperatures that could occur with cooled exhaust gas recirculation compared to combustion in pure air. However, the difference will not be significant.
Christian.